Synthesis and secretion of uteroglobin in rabbit endometrial explants cultured in vitro

Explants from rabbit endometrium incorporate [35S] methionine into uteroglobin and other proteins in an essentially linear fashion for at least 8 h. Newly synthesized uteroglobin was characterized by gel chromatography, sodium dodecyl sulphate gel electrophoresis and immunological techniques. Labelled uteroglobin accumulates in the tissue explants during the first 3 h and then reaches a plateau level. Secretion of uteroglobin into the medium is detected after a 1-h lag period and proceeds linearly thereafter. Explants from animals treated with estradiol alone or estradiol plus progesterone (pseudopregnancy) synthesized respectively 2--3-fold and 10--20-fold more uteroglobin than explants from control animals. The rate of degradation of uteroglobin in the in vitro system was not affected by the hormonal treatment of the animals. There is a good correlation between the uteroglobin content in the uterine fluid and the rate of synthesis of uteroglobin in endometrial explants, suggesting that the in vitro system faithfully reflects the in vivo hormonal effects on uteroglobin synthesis.